The present invention relates in general to frequency-shift keying (FSK) transmitters and receivers, and in particular to a new and useful digital FSK transmitter and receiver and method of operating same.
Frequency-shift keying is a form of frequency modulation used especially in telegraph and facsimile transmission. The modulating wave in frequency-shift keying shifts the output frequency between predetermined values corresponding to the frequencies of correlated sources.
Digital FSK transmitters are known. A digital phase locked loop which can be used as a component of an FSK receiver is also known, but this circuit requires the use of an analog filter to operate as an FSK receiver.
The inventor is not aware of any known instance of a digital FSK transmitter receiver. A digital FSK transmitter receiver would have several advantages over known analog FSK receivers. A digital FSK receiver would allow the use of a gate array rather than a mixed-mode ASIC (Application Specific Integrated Circuit). A gate array implementation is cheaper to develop, requires less turn-around time, and reduces the per part price to less than half that of a mixed-mode ASIC. A digital FSK receiver would also not require a filter which is necessary in analog FSK receivers. This would reduce board area required for the equipment by a factor of two.